The present invention relates to mounts and fasteners. More specifically, the present invention relates to inset panel fasteners which are particularly useful within the aircraft industry.
Many types of mounting devices have been developed for holding one or more objects to a support surface. For example, inset-type fasteners are generally anchored into a structure and include an engagement portion, such as the male or female threads of a screw, for securing objects to the structure. Inset fasteners are particularly advantageous when a strong connection between the structure and object cannot be readily obtained through use of a surface mounted structure.
Sandwich panels are used extensively in the aircraft and marine industries. These sandwich panels typically are made of fiberglass or similar material formed in a honeycomb structure. The honeycomb structure is then typically sandwiched between outer layers of aluminum panels or the like. These sandwich panels are preferred as a result of their relatively inexpensive price, lightweight and high strength. In order to anchor objects to the sandwich panel, inset panel fasteners are typically used. To anchor the inset panel fastener in place, a cavity is typically formed directly through the outer aluminum layer into the honeycomb core using a drill or the like. The inset panel fastener is then positioned within the cavity and an adhesive or other binding material is injected into the cavity to secure the fastener to the honeycomb core. Since the cavity is cylindrical, most inset panel fasteners include a cylindrical barrel having a central bore. The central bore typically includes female threads functioning as a fastener element. Alternatively, some inset panel fasteners include a floating fastener element in the form of a nut which also includes female threads which is floatingly positioned within the bore. Examples of inset panel fasteners including floating elements include U.S. Pat. Nos. 4,973,208 and 5,632,582. Inset panel fasteners have been manufactured from a variety of materials. For example, it has been known to manufacture an inset panel fastener of various metals including steel and titanium. U.S. Pat. No. 4,846,612 describes a one piece inset panel fastener made from a thermoplastic. Moreover, inset panel fasteners have been constructed to include a plastic outer casing and a metal inner fastener element. Unfortunately, the prior art structures and materials have posed problems.
All metal fasteners provide extremely high strength to a fastener element. However, adhesives and potting materials typically do not bond to an all metal material, such as titanium, as well as to a plastic material. They are also heavy and expensive. Meanwhile, inset panel fasteners which include a plastic casing suffer from disadvantages of their own. Plastic fasteners will fracture at lower stress values than all metal inset panel fasteners. Moreover, most plastic inset panel fasteners include a casing constructed into disengageable parts. For example, as shown in U.S. Pat. Nos. 4,973,208 and 5,632,582, the inset panel fastener includes a casing including a cylindrical barrel and a bottom cap. The cylindrical barrel includes a central bore for positioning a female fastener element, preferably constructed of metal. The barrel further includes an opening or entrance formed at the barrel's top for insertion of a male fastener element to engage the female fastener element. Projecting radially from the top of the barrel, the inset panel fastener further includes a disk which has a diameter greater than the diameter of the barrel to form a cavity space around the barrel's body for injection of an adhesive or potting material within the sandwich panel cavity. A fastener element is inserted into the cylindrical barrel's central bore through an access opening located at the bottom of the body. The access opening is then covered by a plastic cap to prevent adhesive material from flowing into the plastic body's central bore which would prevent the fastener element from floating within the inset panel fastener. The cap is typically locked to the cylindrical barrel using a press-fit or locking projections such as shown in U.S. Pat. Nos. 4,973,208 and 5,632,582.
The inset panel fasteners having two part casings are simple to manufacture and inexpensive. Moreover, as a result of the use of locking projections, the casings are simple to assemble. Unfortunately, the inset panel fasteners provide a relatively low pull strength in that the panel fastener will fail and be pulled from the sandwich panel cavity upon a relatively low load being exerted upon the fastener.
Thus, it would be advantageous to provide an improved inset panel fastener which provided improved pull strength.
It would be an additional advantage to provide an improved panel fastener that was manufactured of plastic in a two part casing configuration.
It would be still an additional advantage to provide an improved inset panel fastener that was lightweight, inexpensive to manufacture, provided improved pull strength, and incorporated a floating fastener element.